Just lost my cache disk last night a nvme stick just up and died on me. Furious I lost data like yourself and swore to get dual SSD to do a cache pool. Yet now researching the subject and your own experience as well, it seems a waste of a second drive. Currently looking at a solution myself on a better way of handling the data on cache so if there is a drive failure I don’t lose my data. I use the CA backup appdata plugin but with it having to shutdown dockers it interrupts some of my programs even if it’s running overnight. Also I have a large Plex setup that takes forever to backup. That’s why something like the cache pool would be ideal. Unfortunately it doesn’t perform as advertised. As in actually providing a reliable redundancy for the cache drive.